Prepolymerizer CSTR

The principal difference is that a prepolymerizer CSTR has been placed ahead of the first reactor. An example cited on a production scale similar to the example discussed in Section 2.3.5, reveals the prepol erizer to be a CSTR with a 3-blade agitator operating at 110°C and 7.5% solids. The first reactor is a roughly similar CSTR operating at 125°C and 35% solids. 

Other chemical companies have also designed their own continuous process to produce high-impact polystyrene (HIPS), such as the Dow process, which consists of three elongated reactors in series (US Patent 2727 884, 1955) the BASF process, which consists of a prepolymerization CSTR followed by cascade of three CSTRs (US Patent 3 658 946, 1972) the Shell process, which consists of three CSTRs followed by a plug flow reactor (US Patent 4011 284, 1977) and the Monsanto process, which consists of a CSTR followed by a horizontal plug flow reactor (US Patent 3 903 202, 1975). 

Prepolymerization (4) Prepolymerization is conducted in the first two reactors that are CSTR-type with proprietary agitator designs. Prepolymerization may be thermally or chemically initiated depending on the desired product. For HIPS, this is a critical phase of the process since this is where the rubber morphology and physical properties of the resultant product are controlled. 

High pressure (200-350 MFb) Long reactor (1500 m) Prepolymerization in a CSTR... 

---